More and more federal prosecutors are eschewing a well-worn road to riches in which they decamp to white-shoe law firms to represent the sorts of clients — accused money launderers, swindlers and terrorists — whom they spent years prosecuting.

Instead, a small but growing number of prominent government prosecutors are taking a different route into the private sector, opening their own small law firms that, they hope, will allow them to avoid bureaucracy and nourish an entrepreneurial spirit.

The latest example: Three veteran prosecutors from the United States Attorney’s Office for the Southern District of New York are leaving government practice and will open a boutique firm based in a spare sublet in Midtown Manhattan on Monday.

“On Day 1 we will have zero clients,” said Nicholas J. Lewin, 43, one of the three prosecutors, whose résumé includes trying senior leaders of Al Qaeda and advising Federal Bureau of Investigation leaders. “It’s a bit of a financial cliff jump because you are going from a government salary to no paycheck.”

Mr. Lewin is joined by Edward Y. Kim and Paul M. Krieger. Together, the three have 32 federal jury trials on their résumés.

Such start-up practices used to be unheard-of. Partnerships at major corporate law firms were the default destination for most departing prosecutors. Some lawyers went from jobs at big law firms to stints as government prosecutors before returning to their original employers.

But the trend toward legal boutiques is gathering momentum as elite lawyers aim to preserve the autonomy and power that they enjoyed when working in hard-charging United States attorneys’ offices. At the same time, they can try to lure clients with the promise of more focused, personalized service than they might receive at a firm with dozens or even hundreds of partners.

“I can name 10 firms former prosecutors have started in the last five years,” said Nicole Gueron, a former Southern District prosecutor who helped found the litigation boutique Clarick Gueron Reisbaum in 2010.

“In many ways, being a prosecutor prepares you for your own firm. You’re used to having a lot of authority and making your own decisions,” she said. “And it’s extremely empowering to be the ones who are sailing the ship.”

A similar trend has shaken up the investment banking industry in the last decade. Many veterans of big Wall Street banks have opened or joined boutique financial advisory firms that cater to clients who have grown disillusioned with what they view as inadequate — and sometimes conflicted — services provided by the biggest investment banks. Examples include Moelis & Company, Greenhill & Company and Perella Weinberg Partners.

In the legal world, one appeal of boutiques is that landing jobs in the white-collar practices at top law firms is getting harder. That’s partly because of aggressive hiring in recent years and partly because corporate clients are trying to cut their spending on legal services.

“A lot of firms have filled their white-collar practices. Firms are spending more time to better market themselves, and there is less demand for white-collar attorneys,” said Jack Zaremski, president of Hanover Legal Personnel Services in New York. “There is still a market for highly credentialed lawyers, but big law firms do not have the same need that they once did.”

After working as an assistant United States attorney for the Eastern District of New York, James Walden took a job at Gibson Dunn & Crutcher, a global law firm, where he led its white-collar practice.

After a spell there, Mr. Walden said, “I very much wanted to build something of my own with a strong culture but without the trappings of beautiful paintings or celebrity speakers at retreats, or a lot of internal competition.”

Three years ago, he helped found Walden, Macht & Haran, which specializes in white-collar litigation and government investigations. The firm has grown to 23 lawyers, representing financial institutions as well as cable, media and entertainment companies.

“This is a time when Big Law is at a crossroads,” Mr. Walden said. “We’re trying a new model, which means we can charge about 60 percent of what a Big Law firm would charge for the same services.”

The soon-to-be-opened Krieger, Kim & Lewin plans to adopt a similar lean model. There won’t be secretaries or paralegals. The firm instead will use outside legal research services and contract lawyers, Mr. Lewin said. The goal is to offer high-quality legal work at barely half the price a giant law firm would charge.

His partner, Mr. Krieger, 42, who led the narcotics division in the United States attorney’s office in Manhattan, said, “With less bureaucracy, we will have more freedom to choose the types of matters that we want to handle.”

The trick will be finding clients — a problem they didn’t face as federal prosecutors.

“Entrepreneurship is not for everyone,” said a previous boss of the three prosecutors, the former United States Attorney Preet Bharara. “But these guys are born leaders, not just sharp lawyers, and I expect them to do very, very well.”

Correction:

An earlier version of this article misidentified the founding and growth of the law firm Walden, Macht & Haran. It was started three years ago, not four, and has grown to 23 lawyers, not 24.

Benjamin Weiser contributed reporting.

A version of this article appears in print on , on Page B2 of the New York edition with the headline: A New Route for U.S. Prosecutors: Hanging Out Their Own Shingle. Order Reprints | Today’s Paper | Subscribe

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